How to fix SQLITE_IOERR_UNLOCK: Error releasing file lock in SQLite

Verify that the SQLite process has proper read/write permissions for both the database file and its containing directory:

# Check current permissions
ls -la /path/to/database.db
ls -la /path/to/

# Fix permissions if needed (adjust user/group as appropriate)
sudo chmod 664 /path/to/database.db
sudo chmod 775 /path/to/
sudo chown $(whoami):$(whoami) /path/to/database.db

Ensure the user running the SQLite process has write access to the directory, as SQLite needs to create temporary files and lock files alongside the database.

Check that there is sufficient disk space for SQLite to create lock files and temporary files:

# Check disk space
df -h /path/to/database.db

# Check inode availability (important for file creation)
df -i /path/to/database.db

SQLite needs free space for:
- The main database file (grows during writes)
- Journal files (WAL or rollback journals)
- Lock files (.db-wal, .db-shm, or .db-journal)
- Temporary files during complex queries

Ensure at least 10-20% free space on the filesystem.

Antivirus software can interfere with SQLite file locking. Configure exclusions for your database directory:

Windows Defender:

Add-MpPreference -ExclusionPath "C:\path\to\database\directory"

macOS Gatekeeper/XProtect:
Add the directory to Full Disk Access exceptions in System Settings → Privacy & Security.

Linux (AppArmor/SELinux):

# For AppArmor
sudo aa-complain /usr/bin/your-application

# For SELinux
sudo setsebool -P httpd_can_network_connect_db on

Temporarily disable antivirus to test if it's causing the issue, but always re-enable it after testing.

Network file systems (NFS, SMB/CIFS) often have poor file locking support. Move the database to local storage:

# Example: Copy database from network to local storage
import shutil
import sqlite3

# Copy from network location
shutil.copy2('/network/path/database.db', '/local/path/database.db')

# Connect to local copy
conn = sqlite3.connect('/local/path/database.db')

If you must use network storage:
1. Use NFSv4+ with proper locking support
2. Configure SMB with oplocks disabled
3. Consider using a client-server database (PostgreSQL, MySQL) instead of SQLite for network scenarios

Ensure database connections are properly closed and transactions are managed:

import sqlite3
import contextlib

# Use context managers for automatic cleanup
@contextlib.contextmanager
def get_db_connection(db_path):
    conn = sqlite3.connect(db_path)
    try:
        yield conn
    finally:
        conn.close()

# Use with proper transaction handling
with get_db_connection('database.db') as conn:
    cursor = conn.cursor()
    cursor.execute('BEGIN TRANSACTION')
    try:
        cursor.execute('INSERT INTO users VALUES (?, ?)', ('john', 'doe'))
        conn.commit()
    except Exception as e:
        conn.rollback()
        raise e

Key practices:
- Always close connections in finally blocks
- Use explicit transactions (BEGIN/COMMIT/ROLLBACK)
- Set appropriate timeout values: sqlite3.connect(db_path, timeout=30)
- Limit concurrent connections to the same database

Run filesystem checks and repairs:

Linux (ext4, xfs, etc.):

# Unmount the filesystem first
sudo umount /dev/sdX1

# Run filesystem check
sudo fsck /dev/sdX1

# Remount
sudo mount /dev/sdX1 /mnt

Windows:

chkdsk C: /f

macOS:

# First Aid in Disk Utility, or command line:
diskutil verifyVolume /dev/diskXsY
diskutil repairVolume /dev/diskXsY

Also check for hardware issues with SMART diagnostics:

sudo smartctl -a /dev/sdX